Mechiel Lukkien has made great progress porting native inferno to the SheevaPlug.
Now it's possible to tftp boot an inferno kernel to sh prompt. The Next task is ethernet driver.
For those interested, you can follow the development:
the mercurial repo for kirkwood port is at static-http://www.ueber.net/who/mjl/hg/kirkwood/
the inferno-os code at http://code.google.com/p/inferno-os/source/checkout